ESQL: Meta-ticket for 8.12

[costin]

Description

A meta ticket tracking the main issues we want to solve for the 8.12 release:

New Features

• Async query - ESQL: adding _query endpoint to the Elasticsearch specification #99533
• Cross Cluster Querying (CCS) - Support cross clusters query in ESQL #101640

Language

• Grammar for . fields - ESQL: Improve grammar to allow identifiers with . #100740

Memory tracking

• block ref tracking - ESQL: Make blocks ref counted #100408
• Enrich memory usage - Track ESQL enrich memory #102184

Data loading

• expose source as a metadata field - ESQL: Expose _source as a metadata field #99456
• multi-field extraction at once - ESQL: Visit stored fields once #101322 (ESQL: Load more than one field at once #102192)
• fallback to source extraction for fields that have field data disabled - ESQL: fallback to source extraction for numeric fields that have fielddata disabled #99213

Resilience

• Random generation of random queries - ES|QL: Add random test query generator #102073
• Enrich enhancements -Enhancements for ESQL enrich #101654

Bugs